A water-in-oil emulsion explosive composition typically comprises a continuous fuel phase, a discontinuous phase (oxidizer solution) that is dispersed within the continuous fuel phase, and an emulsifier (stabilizer). This type of explosive may be mixed with ammonium nitrate (ANFO) to form an “emulsion/ANFO” product, which has a higher energy output per unit mass than the original explosive composition.
An emulsion explosive composition may be reduced in density by the addition of gas or air voids, which materially sensitizes the composition to detonation. Gassing solutions are well known in the art and are used to create gas bubbles in the emulsion. The gassing solution typically contains a material that reacts chemically with the oxidizer solution to produce a fine dispersion of gas bubbles. For example, nitrite ions may be provided in the gassing solution to react with the ammonium ions contained in the discontinuous phase (oxidizer solution) to form nitrogen gas bubbles and water.
One disadvantage of current gassing solutions is the need to ensure that the density of the entire emulsion is suitably decreased, and that there are sufficient ‘hot spots’ throughout the emulsion to produce a high velocity of detonation. If the gassing solution is not mixed sufficiently, then the explosive may not explode or it may deflagrate. Another disadvantage of current emulsion explosives that utilize a gassing solution is their limited use at low temperatures. At lower temperatures, the gassing solution may not react sufficiently quickly to sensitize the emulsion explosive prior to detonation. Further, at lower temperatures, the gassing solution may itself freeze, thereby negating the effectiveness of the gassing solution.